BIM Documentation for Existing Buildings: What Is Included

TL;DR: BIM documentation for an existing building is a Revit or IFC model built by a technician from a registered laser scan, showing the building as it stands rather than as it was designed. What it includes is a scoping decision: which disciplines (architectural, structural, MEP), which element types, and what level of development each one is modeled to. The point cloud stays with the project as the evidence behind every modeled element, so the design team can check the model against the scan at any time.

The phrase covers a lot of ground. A facility owner asking for BIM documentation may want a simple architectural shell for space management. A design team planning a plant retrofit may want structural steel and pipe runs modeled closely enough to coordinate new equipment. Both are legitimate, and they cost very different amounts, so the useful question is not "do we need BIM?" but "which elements, to what level, for what use?"

What is BIM documentation of an existing building?

It is a structured 3D model of a building that already exists, created from measured data rather than design drawings. The measured data comes from 3D laser scanning: a scanner records the visible surfaces of the building as a point cloud, the scans are registered into one coordinate system, and a modeler then builds walls, floors, columns, ducts and other elements in Revit using the point cloud as the reference. The industry calls this Scan to BIM.

Two things separate it from a design model. First, it records what is there, including the things that drifted from the original drawings: the wall that is not quite where the plan says, the beam that was added in a past renovation, the duct that runs lower than the ceiling plan suggests. Second, nothing in it is automatic. The scanner produces points, not objects. Every element in the model was placed by a person who made a decision about what it is and how it should be represented, which is why scope and level of development have to be agreed before production begins.

Which elements get modeled?

The scope is usually described by discipline and element type. A typical breakdown:

Discipline	Commonly modeled elements	Typical reason to include
Architectural	Walls, floors, ceilings, roofs, doors, windows, stairs, columns, room boundaries	Space planning, renovation design, area records, fit-out coordination
Structural	Columns, beams, bracing, slabs, foundations where visible	Retrofit design, load path review by the project engineer, clash checks with new work
Mechanical, electrical, plumbing	Ductwork, piping, cable tray, major equipment, sprinkler mains	Routing new services, equipment replacement, coordination in plant rooms and ceilings
Site and exterior	Facade geometry, canopies, exterior stairs, adjacent grade where captured	Envelope work, additions, exterior access planning

Not every project needs every row. An architectural-only model is common for office and retail fit-outs, where the design team needs an accurate shell and partition layout. Industrial projects tend to push into structural and MEP because the existing services are what the new work has to fit around. The industrial facility Scan to BIM project in Calgary is an example where piping and structure mattered more than finishes.

Elements that cannot be seen are not modeled from the scan. Pipes inside a chase, structure above a hard ceiling and anything behind a finished wall are concealed, and a scan-based model should say so rather than guess. Where a project needs those elements, they are either captured during a later phase with the ceiling open, or taken from record drawings and flagged as unverified.

What does level of development mean for an as-built model?

Level of development (LOD) describes how much a modeled element can be relied on for geometry and information. The BIMForum Level of Development Specification is the reference most North American teams use, and it is written for design and construction models, so applying it to an existing-conditions model takes a little translation.

In practice, for scan-based models:

A lower level places elements as generic volumes in the correct location, size and orientation. A wall is a wall of measured thickness and height; a duct is a rectangular run at the measured position. This is enough for space planning, early design and most clash checks against new work.
A higher level adds detail within each element: wall layers where they can be determined, door and window families with measured openings, fittings and connections on pipe runs, equipment modeled closer to its true shape. Production time rises quickly with this detail, so it is worth asking which elements actually need it.

A common mistake is to request one LOD for the whole building. It is more useful, and usually cheaper, to set it by element type: walls and floors to one level, MEP to another, finishes excluded. Our Scan to BIM service page explains how level of detail is confirmed before production, and the comparison in Scan to BIM vs traditional as-builts helps decide whether a model or a 2D drawing set is the right deliverable in the first place.

What stays in the project besides the model?

A good BIM documentation package has three parts, and the model is only one of them.

The registered point cloud. Delivered in a format the design team can load into Revit, Navisworks or a viewer, usually RCP/RCS for Revit users and E57 as the neutral exchange format. Revit links point clouds directly, so the scan can sit behind the model for as long as the project runs. Any question about a modeled element can be answered by looking at the points.
The model. A Revit file in the version the project team uses, or an IFC export for teams on other platforms. IFC is the open exchange format maintained by buildingSMART and is the usual answer when the client's platform is ArchiCAD, Tekla or a facility management system rather than Revit.
A record of modeling decisions. Which areas were inaccessible, which elements were modeled from record drawings rather than scan data, where the scan was thin, and which assumptions were made. This note is what turns a model from a drawing into documentation.

When the owner's goal is to compare the building against a design or construction model, rather than to document it, that is a different service: as-built verification overlays the scan on the model and reports deviations.

How is BIM documentation scoped in Toronto, Calgary and Vancouver?

The method is the same across Canada, but the building stock and the typical project differ by city, and that shapes the scope conversation.

Toronto projects are frequently office, institutional and mixed-use buildings with several generations of renovation layered on top of each other. The scope question is usually which floors and which disciplines, and whether the ceiling space can be opened for MEP capture. See Scan to BIM in Toronto.
Calgary requests skew toward industrial and processing facilities, where structural steel, piping and equipment clearances drive the model and access windows around operations drive the site plan. See Scan to BIM in Calgary.
Vancouver work often involves older timber and masonry buildings with irregular geometry, heritage elements and seismic upgrade planning, where the point cloud is as valuable to the structural engineer as the model is to the architect. See Scan to BIM in Vancouver.

In every case, the project engineer or architect decides what the model is for. On-Site Measurements produces the measured model; it does not provide engineering analysis, stamped drawings or design services.

What should you send to get a quote?

Scoping goes fastest when the request includes:

the site address, building type and approximate area, with the floors or zones to include;
the disciplines and element types you want modeled, and any you want excluded;
the level of development by element type, or a description of what the model will be used for so a level can be proposed;
the Revit version your team is on, or the platform if it is not Revit;
whether ceilings can be opened and when the building can be accessed;
any existing drawings or models, even outdated ones.

From that, you receive a fixed-scope quote within 24 hours that states which elements are included, the level they are modeled to, the formats delivered and what is excluded.

Frequently asked questions

Is BIM documentation the same as as-built drawings?

No. As-built drawings are 2D plans, sections and elevations drafted from the scan. BIM documentation is a 3D model with elements that carry information. Both come from the same point cloud, and many projects order drawings first and add a model later if the project needs one.

Can the model be linked into our own Revit project?

Yes. The model is delivered as a Revit file in your project's version, with the point cloud as a linked RCP where that was in scope. Shared coordinates and level names are agreed during scoping so the link lands where you expect it.

Do you model from the scan or from old drawings?

From the scan. Where an element could not be captured, it is either excluded or modeled from record drawings and flagged as unverified in the delivery notes.

How accurate is the model?

Model accuracy depends on the scanner and field workflow, the site conditions, scan coverage and the level of development agreed for each element. No single tolerance applies to every project, so accuracy expectations are discussed during scoping rather than quoted as a number.

Can we start with one floor or one discipline?

Yes. Many owners document the architectural shell first and add structural or MEP scope for the areas where a project is planned. The point cloud from the first visit can be reused if the later scope falls within what was captured.

BIM Documentation for Existing Buildings: What a Revit Model of an Existing Building Includes